The invention relates to the horticultural and agricultural field and more particularly to methods for killing, controlling or otherwise impacting the life cycle of insect pests found on agricultural and horticultural products. The term xe2x80x9cagricultural and horticultural productsxe2x80x9d as used herein refers to (1) plants that are raised for their esthetic appearance as well as (2) plants and parts of plants that are cultivated or raised for food including the fruits or any part of such plants both before and after separation from the rest of the plant in addition to (3) the plants and parts of plants that grow wild. Thus, the invention has application to all plants, all fruits that are grown on plants, all cut flowers, or any part of a plant although the invention is not limited to controlling insects on these products.
Pesticides are an important component to agricultural production throughout the world. Pest control pertains to a wide range of environmental interventions that have their objective to kill or reduce to acceptable level insect pests, plant pathogens and weed populations. Specific control techniques include chemical, physical and biological control mechanisms. It has been estimated that pest annually destroy about 35% of all food crops before they are harvested and another 10-20% loss is incurred after the food is harvested.
Chemical controls include chemical agent pesticides that include herbicides, for the control of weeds, insecticides for the control of insect pests and fungicides for the control of soil and plant pathogens that include bacteria, fungi and viruses. Herbicides account for over half of the pesticides that are uses world wide, with 30-35% of pesticide production in the form of insecticides and the balance for the production of fungicides.
It is important to control populations of insects that affect ornamental and agricultural crops and inflict major damage to the crops resulting in crop loss. Insects can either directly affect crop loss by either feeding on the crop itself, they either damaging the plant from producing a fruit or tuber, such as a potato plant or indirectly by either sucking the juices out of a plant that directly affects the aesthetics of the plant, which in the case of ornamental crops such as cut flowers and house plants make the crop unsaleable.
Insects are also a major cause of the spread of infectious disease from plant to plant. As insects feed on the flowers and leaves of the plant, they pick up and transmit potentially deadly pathogenic disease organisms such as bacteria and fungi that are then transmitted to another plant when the insect either crawls on the plant, deposits feces or eats portions of the plant.
Most modern day insecticides are comprised of long lasting, synthetic compounds that affect the nervous system of insects on contact. Among the most effective are the chlorinated hydrocarbons, such as chlordane, and toxaphene and other organophoshates that include malathion, parathion, and dimethoate.
While these pesticides have prove to be very effective at controlling insect pests they have also contributed to an unacceptable environmental cycle that directly affects human health and welfare as well as direct and indirect environmental damage. Modem day insecticides primarily work by placing a poison or toxin residue on the surface of plant tissue or by directly spraying the insect pest with the poison compound.
With a typical insecticide the insect comes into contact with the toxic substance by either being directly sprayed or landing on the residue that has been placed on the plants surface or in the soil in which the plant is ground. The toxin is then either ingested, or enters the insects body through its pores. The toxin then either interferes with the insect""s nervous system or other bodily functions such as making it sterile or incapable of eating. Eventually, the insect dies, if the toxin is not deadly enough to produce an immediate kill.
There are several problems that arise from using chemical insecticides. They include resistance, human toxicity, and environment damage.
Since traditional insecticides work on the principal of chemical toxicity, the insect is capable through genetic mutation of developing a resistance to the toxins that affect it. In the insect world, where generations are produced in the pans of weeks, the problem of genetic resistance is common. Within a very short amount of time, many insects that were formally susceptible to certain chemical compounds, find that sometimes within the span of a few years, the chemical either does not produce a kill or the dosage must be increased to produce a kill.
This is why insecticide applicators must cycle their applications of different chemical compounds so as not to allow insects they are trying to control to become accustom to any one chemical compound and ultimately to become immune to the chemical. This practice of chemical rotation is both times consuming and expensive, since the applicators must have at minimum three different chemical compounds for various types of insect pests.
Most chemical insecticides must be used and applied with extreme caution. Typically, the applicator must at all times wear special protective personal protection clothing. This includes the use of respirator and eye protection, as sell as chemical impervious coveralls and gloves. Since the insecticides produce a toxic residue and are by nature long lasting and complex compounds, over a period of time, direct exposure to insecticides can lead to human health concerns and in some cases direct exposure to certain insecticides can lead to toxic shock and death.
Due to the very nature of the insecticide that is designed to leave behind a toxic residue on either plant surfaces or in the soil, environmental damage is a direct concern. There has been increasing concern about the impact of groundwater by complex pesticide compounds that do not break down into innocuous substances. It has been documented that pesticide compounds have directly impacted groundwater aquifers and directly threated environmental security.
In addition to concerns about groundwater impacts, insecticides often impact non-target organisms within the environment that come into contact with the insecticide. These organisms include fish, birds, other non-pest insects, and all forms of animal life. There have been hundreds of documented cases of insecticides such as DDT and others entering the food chain and impacting birds such as the American bald eagle, storks, rainbow trout and others.
Because of the problems associated with the use of traditional chemical insecticides a need exisits for a safe method to control insect pests commonly found in commerical horticulture and agriculture.
An object of the present invention is to provide a safe method of controlling insect populations through either direct killing or by killing of insect larvae and food sources
It is an another object of the present invention to provide a method to control insect populations that is safe and convenient to use.
It is another object of the present invention to provide a method of controlling insect pests, which reduces worker exposure to hazardous and toxic compounds.
It is yet another object of the present invention to provide a method of protecting plants from insect infestations through the entire life cycle of the plant.
It has now been found that these and other objects of the invention may be attained in a method for control of insects which includes applying a solution of hydrogen peroxide to plant tissue, said hydrogen peroxide being a solution having a concentration of between 0.05 to 3.00%.
In some cases the hydrogen peroxide solution has a concentration of between 0.05 and 1.5%. Some forms of the invention may utilize a hydrogen peroxide solution that further includes an acid selected from the group consisting of acetic acid and phosphoric acid.
In some cases the hydrogen peroxide solution is applied to the plant tissue at a variety of stages in the plant production cycle. Other application of the invention include applying misting the hydrogen peroxide solution over terminal stem cuttings until they reach root sufficiency.
The method in accordance with the invention utilizes hydrogen peroxide, sometimes known as peroxygen, for the purpose of killing the most common plant pathogens in greenhouses, lawns, gardens, orchards, forests, and other agricultural crops. It was discovered that when a dilute solution of hydrogen peroxide is applied to living plants by spray, mist, fog or immersion (including the root system), the plant pathogens present on the surfaces were either totally eradicated or substantially reduced. The plants suffered no adverse affects from the treatment. Daily treatments with hydrogen peroxide had no adverse effect upon the health of the plants. There were no signs of discoloration of the flowers on ornamental plants. The most obvious effect was the elimination of the fungi, particularly on the plant leaves and stems since fungi are extremely visible on these areas. The effect of the hydrogen peroxide upon pathogenic bacteria and viruses were not observed since these diseases are relatively uncommon. However, the effects of hydrogen peroxide upon bacteria and viruses has been well documented in the literature and one could expect the same sanitizing effect upon these agents as was observed upon the more resistant fungal agents. The important point to remember is that hydrogen peroxide is a very powerful disinfectant and yet does not harm delicate plant tissues when used at a concentration lethal to the plant pathogens. Other added advantages of hydrogen peroxide disinfection are, the lack of a residue upon the treated surfaces, and the totally innocuous breakdown products of water and oxygen which are readily absorbed by the plants.
Still another surprising advantage of the application of even the moderate concentration of hydrogen peroxide that will not harm delicate plant tissue is that this moderate concentration will substantially reduce the population of insects in the plant environment. Since insects are a source of plant diseases and even the presence of insects on plants make the plant unsuitable for sale. Plants having an infestation of insects are even worse than being unsuitable for sale in that if any such plants were to reach any retail or wholesale customer for such plants it is unlikely that the customer will quickly purchase any additional plants from the same supplier.
The invention may usually be attained in a method in which a hydrogen peroxide solution of between 0.05% and 3.0% is applied periodically to the plant material throughout the plant production cycle. The method permits the hydrogen peroxide solution to be applied to the plant material continuously and or periodically during this time period without adversely affecting the plant growth.
More particularly, a solution of hydrogen peroxide diluted with water to a total hydrogen peroxide concentration of about 0.05 to 3.00 percent is preferred. A solution of about 1.0% hydrogen peroxide is preferred for initial application to plant tissue already infected with microorganism while a solution of about 0.05% is preferred for repeated applications intended to protect plant tissue from microbial infection. The addition of acetic or phosphoric acid to the solution at a concentration of about 0.05% is useful to stabilize the hydrogen peroxide solution in certain water conditions. Any commercial source of hydrogen peroxide solution may be used to carry out the method of the present invention. Typical concentrations commercially available are between 3 and 70 percent hydrogen peroxide. While any of these forms will work in the present invention, it may be more convenient in some cases to purchase a 50% concentration and then dilute that solution down to the appropriate concentration in accordance with the present invention. One method which may be useful for diluting concentrated solutions is to use a Dosatron(trademark) Proportioner made by Dosatron International, Inc.
The solution may be delivered to the plant tissue by standard pesticide application techniques. High volumes may be applied by hydraulic spraying and low volumes may be applied by misting or fogging. The solution may also be applied by injecting the hydrogen peroxide into a commercial cooling system. Alternatively, the hydrogen peroxide may be injected into a recirculating subirrigation nutrient system solution to control microbial growth in the irrigation water.
The hydrogen peroxide solution may be applied to the plant tissue at a variety of stages in the plant production cycle. This is illustrated by ever present problem of Botrytis cinerea foliar and stem blight experienced in all zonal geranium propagation. By injecting hydrogen peroxide solution into the water that is misted over the terminal stem cuttings until they reach root sufficiency surface microbial contaminants, including most notably Botrytis, will be reduced. This will dramatically reduce the cost of propagating this crop by reducing plant mortality, plant handling and fungicide applications.
Another unexpected result of the field trials with the hydrogen peroxide product was the lethal effect it had upon the insect pest that were present in the greenhouse. The insect pests that were adversely affected by the peroxide treatment were, mealy bug, aphids, spider mites, white fly, fungus gnats, and thrip. The effects of the hydrogen peroxide appear to be upon the embryonic stages of the insects except for fungus gnats which disappeared probably because of the removal of the fungus in the greenhouse which is their source of food. Because of the short life time of most insects and the vulnerability of insects in the embryonic stages the treatment is highly effective.